DOVER — The Monarch Butterfly, arguably one of the most beautiful and popular of all insects is on the decline across North America. Why?

Published reports like a NHPR story on March 14 of this year tell a tale of their population decrease in Mexico, the Monarch winter home. According to NHPR, scientists report that where the fluttering creature once inhabited over 50 acres in central Mexico they now only have the numbers to fill about 3. As late as 2011 the butterflies inhabited just over 7 acres of forest, according to the Mexico National Commission for National Protected Measures.

The Monarch migrates to central Mexico from the Northern U.S. and Canada. The report went on to say that there is a decrease in the butterfly’s habitat throughout the Midwest, due at least in part to the genetically modified, herbicide tolerant crops that allow farmers to wipe out milkweed and thus eliminating the preferred breeding ground for the Monarch.

According to Wikipedia’s Monarch online page, Chip Taylor, Director of the University of Kansas’ conservation group Monarch Watch, says the milkweed habitat is “virtually gone” from the Midwest. That’s a reported loss of 120-150 million acres.

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A Monarch Caterpillar. (Courtesy photo)

An invasive plant from Europe, black swallow wort, has also been cited as a possible reason for the population decrease. The plant secretes similar stimuli as the native milkweed, prompting the Monarchs to lay their eggs on that plant. After the caterpillar emerges, however, it is killed by the toxicity of the plant when it feeds.

Here in New Hampshire, UNH Cooperative Extension etymologist Alan Eaton said he hadn’t noticed a decrease in population locally. The fluttering winged insects that bring joy to many children and adults are not expected to arrive here until August or September, but “Everywhere I expected to see them last year I did,” Eaton told Fosters. He also said he doesn’t know of anyone in this area who conducts regular counts.

Emily Preston, a wildlife biologist with NH Fish and Game said the swallow wort is certainly a plant to watch out for. While it isn’t considered to be prominent in the Granite State just yet, she did say the invasive plant has been seen along the seacoast.

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A Monarch Butterfly. (Courtesy photo)

Preston said that while she doesn’t consider the plant to resemble the milkweed in the physical sense, there is something which attracts the Monarch. The state is in the process of putting together a study of invasive plants, like the wort, to inform towns and residents of which plants are affecting the native plants.

According to the site, in 2012, there was a record low of 60 million counted, down from the average of 350 million. They cite the record heat during the summer of 2012, harsh winter and late spring as reasons for the decline. Such weather patterns will slow the migration of the Monarch north from Mexico, where they typically have four breeding grounds on the way to Canada and the Northern U.S., and may lead to a missed generation.

The Monarch Butterfly makes a yearly journey from Central Mexico, where it winters, up through the US and into Canada for the summer, stopping several times along the way to breed the next generation. They return to Mexico in the fall for the winter in warm climates.

A report from the Canadian News Wire filed on July 18, cited experts seeing a 90 percent decline in the population across eastern Canada. That certainly would translate to a scarcity in New Hampshire and New England as they make their annual pilgrimage south.

Such a dramatic drop in the population will have an effect on the ecological system.

“They are certainly part of a complex food web,” Preston said. However, it is incredibly difficult to discern whether such a loss of a species, should that occur, would cause a major or minor ripple effect in the overall ecosystem.

Because there are no official Monarch counting programs in place in New Hampshire, all officials here can do is wait and hope that those who alight in the Granite State are as visible as they have been in the past.